mmc: sdhci: if MAX_CURRENT is 0, try getting current from regulator

The sd host controller spec indicates the the MAX_CURRENT value may
be returned as 0.  In this case other methods need to be used to
return the current.  If 0 is returned and there is a regulator,
ask the regulator for how much current is available.
Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Mark F. Brown <mark.brown314@gmail.com>
Reviewed-by: Aaron Lu <aaron.lu@amd.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -2837,6 +2837,13 @@ int sdhci_add_host(struct sdhci_host *host)
 			     SDHCI_RETUNING_MODE_SHIFT;
 
 	ocr_avail = 0;
+
+	host->vmmc = regulator_get(mmc_dev(mmc), "vmmc");
+	if (IS_ERR(host->vmmc)) {
+		pr_info("%s: no vmmc regulator found\n", mmc_hostname(mmc));
+		host->vmmc = NULL;
+	}
+
 	/*
 	 * According to SD Host Controller spec v3.00, if the Host System
 	 * can afford more than 150mA, Host Driver should set XPC to 1. Also
@@ -2845,6 +2852,21 @@ int sdhci_add_host(struct sdhci_host *host)
 	 * value.
 	 */
 	max_current_caps = sdhci_readl(host, SDHCI_MAX_CURRENT);
+	if (!max_current_caps && host->vmmc) {
+		u32 curr = regulator_get_current_limit(host->vmmc);
+		if (curr > 0) {
+
+			/* convert to SDHCI_MAX_CURRENT format */
+			curr = curr/1000;  /* convert to mA */
+			curr = curr/SDHCI_MAX_CURRENT_MULTIPLIER;
+
+			curr = min_t(u32, curr, SDHCI_MAX_CURRENT_LIMIT);
+			max_current_caps =
+				(curr << SDHCI_MAX_CURRENT_330_SHIFT) |
+				(curr << SDHCI_MAX_CURRENT_300_SHIFT) |
+				(curr << SDHCI_MAX_CURRENT_180_SHIFT);
+		}
+	}
 
 	if (caps[0] & SDHCI_CAN_VDD_330) {
 		int max_current_330;
@@ -2995,12 +3017,6 @@ int sdhci_add_host(struct sdhci_host *host)
 	if (ret)
 		goto untasklet;
 
-	host->vmmc = regulator_get(mmc_dev(mmc), "vmmc");
-	if (IS_ERR(host->vmmc)) {
-		pr_info("%s: no vmmc regulator found\n", mmc_hostname(mmc));
-		host->vmmc = NULL;
-	}
-
 	sdhci_init(host, 0);
 
 #ifdef CONFIG_MMC_DEBUG

drivers/mmc/host/sdhci.h

@@ -205,6 +205,7 @@
 #define SDHCI_CAPABILITIES_1	0x44
 
 #define SDHCI_MAX_CURRENT		0x48
+#define  SDHCI_MAX_CURRENT_LIMIT	0xFF
 #define  SDHCI_MAX_CURRENT_330_MASK	0x0000FF
 #define  SDHCI_MAX_CURRENT_330_SHIFT	0
 #define  SDHCI_MAX_CURRENT_300_MASK	0x00FF00